FirebaseAuth firebaseAuth = FirebaseAuth.getInstance(); firebaseAuth.signInWithEmailAndPassword(email, password).addOnCompleteListener( new OnCompleteListener<AuthResult>() { @Override public void onComplete(@NonNull Task<AuthResult> task) { if (task.isSuccessful()) { startActivity(new Intent(SignInActivity.this, MainActivity.class)); finish(); } else { Snackbar .make(root, task.getException().getLocalizedMessage(), Snackbar.LENGTH_LONG) .show(); } } });